如何使用jquery正确地将<select>添加到页面并让更改事件有效？

<script src="https://code.jquery.com/jquery-3.6.0.min.js"></script>

$(document).ready(function() {
  $('#mySelect').init({ selected: 'my-value' });
});

$(document).ready(function() {
  $('#mySelect').init({ selected: 'my-value' });
  $('#mySelect').on('change', function() {
    alert($(this).val());
  });
});

from flask import render_template
from flask import request

app = Flask(__name__)

@app.route('/')
def my_select_view():
  return render_template('select_form.html')

@app.route('/results', methods=['POST'])
def my_select_results():
  dropdown = {'my-value': 'Selected value'}
  return jsonify(dropdown)

document.getElementById('mySelect').options[0].selected = true;
document.getElementById('mySelect').options[1].selected = true;
document.getElementById('mySelect').options[1].onmousedown = function() {
  alert('Option selected. Value: ' + this.value);
};